1. Field of the Invention
This invention relates to a method and apparatus for measuring the mass of fibrous particulates being transported through or with a gaseous medium.
2. Description of the Prior Art
Several apparatus are available for determining the mass of particles being transported in or through a gas. Green et al. ("A Low Cost Solids Flow Meter for Industrial Use,"Journal of Physics E: Scientific Instruments, Vol. 22, No. 10, October, 1978, pp. 1005-1010), describes an instrument for measuring the mass flow rate of dry conducting or nonconducting granular solids or powder. As solids are transported into and through a capacitor formed by the walls of a conveyor, the dielectric constant of the air in the field of the capacitor changes and the change is converted to an electrical signal that may be correlated with the mass flow of the solids.
West German Auslegeschrift No. 1,121,822, issued on Jan. 11, 1962, to Moller et al., discloses an apparatus for measuring the quantity of material conveyed in a gas through a pipeline. A wire extends along the axis of the pipeline, and an electric field is produced between the wire and the pipe wall. The wire is connected to a capacity-measuring bridge, and changes in the electric field are related to the solids flow between the wire and pipe wall.
U.S. Pat. No. 4,312,180 issued to Reif et al. on Jan. 26, 1982, and entitled "Detecting Particles," describes an apparatus comprising a pair of electrically conductive members spaced apart and means for providing an electrical potential adjacent one of the members. This potential produces ions which transmit a charge to particles being transported past the ion-producing member. The charged particles are moved downstream within the apparatus and detected by charge detecting means.
Also somewhat related is U.S. Pat. No. 3,478,261 to Forster et al., which teaches a means for measuring static charge in a pipe carrying a liquid hydrocarbon steam comprising a pair oppositely-charged electrodes in the pipe, a bias voltage source, a ground connected to the negative side of the bias voltage, and a pair of electrometers between the electrodes and the ground. The algebraic sum of the currents flowing from the two electrodes to the ground indicates the amount of static charge.
However, none of the prior art teaches a simple means for detecting the mass flow rate of particles in a conduit by simply measuring electrostatic current resulting from static charge formation.